Sulfonated permeable membranes capable of selectively permeating one component of a fluid mixture, either liquid or gas, from a mixture thereof with other components, are considered in the art as a convenient, potentially highly advantageous means for achieving components separations. For practical commercial operations such membranes must be capable of achieving an acceptable level of separation, or selectivity, of the desired component contained in the fluid feed stream while, at the same time, achieving a desirably high productivity, or permeability rate, of component separation.
Various types of permeable, or semipermeable, membranes are known in the art for carrying out a wide variety of fluids separations. Such membranes have been classified as being of the isotropic, composite, or asymmetric types, their structures being well known in the art.
This invention relates to certain sulfonated fluorinated polysulfones resins, their preparation and use; and more particularly to cation exchange resins derived from specific fluorinated polysulfones, membranes derived from such resins, and their application.
Sulfonated polysulfones are known in the art as useful, chemically resistant ion-exchange resins. The preparation of sulfonated polyarylether sulfones is described by J.P. Quentin in U.S. Pat. Nos. 3,709,841 and 4,054,707, and further examples of preparation of sulfonated polysulfones can be found in U.S. Pat. Nos. 4,268,650; 4,273,903; 4,414,368; and 4,508,852.
Additional disclosures on preparation of sulfonated polysulfone membranes can be found in U.S. Pat. Nos. 4,717,395; 4,207,182; 4,026,977; 3,875,096; and 3,855,122.
In an article by A. Noshay and L.M. Robeson, "Sulfonated Polysulfone", J. App. Pol. Sci., 20, 1885-1903 (1976), the use of a sulfur trioxide/triethyl phosphate complex as the sulfonating agent is reported.
Among the polymers known to be useful permeable membrane materials are the sulfonated bisphenol-A polysulfones having the polymer repeat unit: ##STR3## It has now been discovered that when the ##STR4## radical in the polymer backbone is replaced by the ##STR5## radical, substantial improvements in membrane forming characteristics, in chemical durability and in gas permeation rate occur to provide membranes with unexpected and unpredictable improved permeation and separation characteristics.
The sulfonated polysulfone materials of this invention can be advantageously used in numerous membrane separation processes, such as gas separations, reverse osmosis and ultrafiltration processes; electrochemical membrane separations, such as electrodialysis as a dialysis membrane; and as battery separator membranes.